Optical pulse propagation in resonantly absorbing medium and a new definition of group velocity

光脉冲在共振吸收介质中的传播和群速度的新定义

• 批准号: 14540375
• 负责人: TOMITA Makoto
• 金额: $ 2.37万
• 依托单位: sizuoka university
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 2002
• 资助国家: 日本
• 起止时间: 2002 至 2003
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-14540375/
• 关键词: pulse propagation; group velocity; anomalous dispersion; superluminal

The purpose of the present research is to establish a new definition of a group velocity : which has a good meaning even in the long pulse propagation distance where the conventional definition of the group velocity breaks down, This new definition takes the effect of the imaginary part of the refractive index into account. The imaginary part, which inevitably exists owing to the Kromas-Kronig relation, is very essential in the pulse propagation in the resonant regions. Chirped pulses show a large Reshaping Delay owing to the spectral shift caused by the imaginary part of the refractive index. In incoherent pulses, there was no way to discuss the pulse velocity. In the present research, we define the position of the incoherent pulses by the centre of gravity, and discussed the meaning of the propagation velocity. While the Reshaping Delay in the individual incoherent pulses appears randomly, this delay is the ensemble averaged and the pulse propagates with a Net Delay.In order to verify the above theoretical predictions, we constructed an experiment system based on a modified Michelson interferometer and a TiO2-Safire laser, and performed systematic experiments on the femtosecond pulse propagation. Form these results, we consider that the new definition of the group velocity has well meaning even in the phase modulated pulses.

本研究的目的是建立群速度的新定义：即使在群速度的传统定义失效的长脉冲传播距离中，该定义也具有良好的意义，这个新定义利用了虚部的影响考虑折射率。由于 Kromas-Kronig 关系，虚部不可避免地存在，它对于谐振区的脉冲传播非常重要。由于折射率虚部引起的光谱偏移，啁啾脉冲显示出较大的整形延迟。在非相干脉冲中，无法讨论脉冲速度。在本研究中，我们通过重心定义非相干脉冲的位置，并讨论了传播速度的含义。虽然各个非相干脉冲中的整形延迟是随机出现的，但该延迟是整体平均的，并且脉冲以净延迟传播。为了验证上述理论预测，我们构建了一个基于改进的迈克尔逊干涉仪和TiO2的实验系统-Safire激光，对飞秒脉冲传播进行了系统实验。从这些结果来看，我们认为群速度的新定义即使在相位调制脉冲中也具有很好的意义。

项目成果

Toru Ito, Makoto Tomita: "Reshaping delay in chirped pulse propagation"International workshop on femtosecond technology. EST2002. 200-200 (2002)

Toru Ito、Makoto Tomita：“重塑啁啾脉冲传播的延迟”飞秒技术国际研讨会。

Tetsu Ito, Takatoshi Haruta, Makoto Tomita: "Laser action in a two-dimensional random medium"International workshop on femtosecond technology. FST2003. 170 (2003)

Tetsu Ito、Takatoshi Haruta、Makoto Tomita：“二维随机介质中的激光作用”飞秒技术国际研讨会。

Makoto Tomita: "Coherence coupling effect in a space and time resolved nonlinear correlation measurement in a disordered medium"Journal of the Optical Society of America. B21. (2004)

Makoto Tomita：“无序介质中时空分辨非线性相关测量中的相干耦合效应”美国光学学会杂志。

Tetsu Ito, Takatoshi Haruta, Makoto Tomita: "Laser action in a two-dimensional random medium"International workshop on femtosecond technology FST2003. 170 (2003)

Tetsu Ito、Takatoshi Haruta、Makoto Tomita：“二维随机介质中的激光作用”飞秒技术国际研讨会 FST2003。

Tetsu Ito, Makoto Tomita: "Speckle correlation measurement in a disordered medium observed through second harmonic generation"Physical Review. E69. 36610-1-36610-7 (2004)

Tetsu Ito、Makoto Tomita：“通过二次谐波产生观察到的无序介质中的散斑相关测量”物理评论。